Electrodeposition of uranium oxide



United States Patent 9 2,784, 86 ELECTRODEBOSITIDN QEURANIUMOXIDE Alois Langer and Carl R; Wilson, Pittsburgh, v, Pa, as-

signors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation oEPennsylvania.

No Drawing. ApplicatiomMarch. 17., 1953,

Serial No-.. 342,995

5 Claims. (Cl. 29-195) This invention relates to the-electrodeposition of uranium oxide on aluminum and magnesium surfaces.

It has been discovered that known techniques for resultin satisfactorily coating of uranium oxideon nickel or platinum, fail toproduce satisfactory coatings. of

uranium oxideon aluminum and magnesium surfaces.,

highly adherent on the aluminum magnesium. surfaces so that they will withstand vibration, shock and expected wear and tear. Furthermore, such coatings should be ofsubstantially uniform thickness, over the desired sur-.

faces of the aluminum and magnesium in order to produce satisfactory results as fission counter elements.

The object of the present invention is. to provide for electrodepositing satisfactory uniformly thick uranium oxide coatings on aluminum and magnesium surfaces, such coatings being highly adherent and durable.

A further object of the invention is toprovide for electrodepositing a predetermined. weight-i of uranium oxide. over selected surfaces of aluminum and magnesium.

A still further object of the invention is to provide members of aluminum or' magnesium having a substantially uniformly thick coating of uranium oxide, such coatings being highly adherent and durable to withstand vibration and shock.

Other objects of the invention will, in part, be ob-- vious, and will, in part, appear hereinafter. For a better understanding of the nature and objects of the invention, reference should be had to the following detailed description.

We have discovered that substantially uniformly thick coatings of uranium oxide may be electroplated upon aluminum and magnesium surfaces by the following procedure: (1) Cleaning the surfaces of the alumnium or magnesium, (2) depositing a thin layer of zinc on the cleaned aluminum or magnesium surface, and (3) plating the zinc coated aluminum or magnesium member in a specific electrolyte containing uranyl ions, as will be disclosed hereinafter. In cleaning the aluminum or magnesium, the metal is preferably degreased in a solvent, either in the liquid or vapor phase or both. Suitable solvents are organic solvents, such as esters, alcohols, and chlorinated ethylene compounds. Subsequently, it is desirable to dip aluminum members in a hot solution of sulfuric acid. Magnesium is extremely difficult to clean chemically and We have found that an excellent procedure is to sand blast the surfaces of the magnesium with a fine abrasive, such as 100 mesh alumina.

It will be appreciated that the aluminum and magnesium members may be in the form of discs, plates, sheets, tubes or Wire. One of the merits of our invention is that large members, for example, sheets of an area 2,784,486 Patented Mar. 12,, 19.57

2' of several hundred square centimeters, may be readily coated with uranium oxides with complete success- In treating tubes care should be taken to thoroughly clean the interior of tubes as well as the exterior surfaces.

If it is desired, parts of the aluminum or magnesium members may be masked or screened to expose only those portions that are to be plated'with the uranium oxide. Masking lacquers are well known in the art and may be applied to the magnesium or aluminum surfaces by hand or through a screen or the like.

In treating the aluminum members, they are dipped, immediately after degreasing and cleaning, in a. zincatesolution comprising from 10.to 13 ounces per gallon of.

zinc oxide and 55 to 70 ounces per gallon of. caustic soda. The immersion in the zincate'solution, may be. for only 15. to 30 seconds and not over about one minute- As aresult of the immersion in the zincate solution, a thin layer of zinc, less than 0.0001 inch, is deposited over all of the exposed aluminum surfaces.

The aluminum member is removed from the. zincate solution, rinsed in distilled; water and then placed in the following electrolyte. An electrolyte is prepared by dis.- solving in distilled water at least, 5. grams per liter of ammonium oxalate. A weighed quantity of a water soluble uranyl salt, such', for example, as uranyl acetate or uranyl nitrate, is dissolved in the oxalate solution, and ammonia is added to bring the pH to a value from about 8 to 8.5. The uranyl salt may be comprised of any isotopic composition of uranium. The solution so prepared is heated to atemperature from about C. to C. The Zinc coated member is made the cathode in this electrolyte. A platinum anode is then introduced into the electrolyte and an electric current is passed through the zinc coated aluminum member at a density of from 5 to amperes persquarefoot. The anodes may be distributed within tubes or otherwise disposed to follow good plating practice. The electrical current is passed until all the uranium added to the electrolyte has been plated out as uranium oxide on thezinc. coated aluminummember. This. insures the desired weight of uraniumoxide being platedon the members. The following example illustrates the plating of an aluminum member.

Example I A disc of aluminum of an area of approximately 10 square centimeters is degreased in a solvent .vapor apparatus employing chlorinated ethylene. The cleaned aluminum disc is rinsed in distilled water and then dipped into hot 25% sulfuric acid for 1 minute. The aluminum disc is then rinsed thoroughly in distilled water and then immersed in an aqueous zincate solution comprising 12 ounces per gallon of zinc oxide and 60 ounces per gallon of caustic soda. The disc is immersed for 30 seconds in the zincate solution which is stirred during the immersion. A uniform gray coating of zinc is deposited on the aluminum. The zinc coated aluminum member is rinsed in distilled water and then made the cathode in an electrolyte comprising 14.2 grams per liter of ammonium oxalate and 30 milligrams of uranyl acetate. Platinum Wire is made the anode in the electrolyte. An electrical. current at a density of 50 amperes per square foot of the zinc coated aluminum is passed through the electrolyte. The plating is conducted for about 45 minutes and essentially all of the uranium in the electrolyte is deposited as a uranium oxide coating uniformly over the zinc plated disc of aluminum at about 2 milligrams per square centimeter of surface. The oxide is found to consist essentially of U308- If desired, the disc may be heated in an oven at temperatures of up to 400 C. to 500 C. to dry the film. The adheren e is not affected by the heat treatment.

Tests have been made by employing vibration and heavy shocks. In no case did the uranium oxide coating on the aluminum chip or break off.

By following the indicated procedures, there may be deposited uniformly thick uranium oxide coatings of densities of from 0.1 milligram per square centimeter of up to 5 milligrams per square centimeter of aluminum surface. Both thinner and heavier coatings can be applied if desired.

It has been found that the zincate coating treatment does not produce the best base for uranium oxide plating of magnesium surfaces. We have secured best results by placing cleaned and sand blasted magnesium members in aqueous solutions, comprising from 20 to 60 grams per liter of zinc, from 20 to 120 grams per liter of alkali metal cyanide, and from 30 to 120 grams per liter of alkali metal hydroxide, the ratio of the weights of the alkali metal cyanide to the zinc being from about 2 to 3. The sand blasted magnesium member is plated for a period of time not exceeding a minute of a current density of at least 40 amperes per square foot of magnesium surface. It is desirable that the cathode leads be attached to the magnesium member before it is immersed in the zinc cyanide solution. Under these conditions, an extremely thin uniform coating of zinc is deposited. The coating of zinc is of the order of 0.00001 inch in thickness. The magnesium member with the zinc coating thereon is withdrawn from the electrolyte, rinsed in distilled water andis then plated with uranium oxide in the uranyl ion containing electrolyte previously described for the treatment of aluminum members. Similar successful results are obtained.

The magnesium member with the electrodeposited uranium oxide coating may be employed for fission counters and the like. It has been found that the uranium oxide coating on the magnesium is adherent and resists disruption from shock or vibration.

It will be understood that the above description is not exhaustive, but is illustrative of the practice of the invention.

We claim as our invention:

1. In the process of plating adherent durable coatings of uranium oxide on the surface of a member of a metal from the group consisting of aluminum and magnesium, the steps comprising depositing a thin layer of zinc on the clean surfaces of the member, making the member a cathode in an electrolyte comprising essentially an aqueous solution containing at least 5 grams per liter of ammonium oxalate and an amount of a water soluble uranyl salt suflicient to deposit a desired weight of uranium oxide on the zinc coated member, the aqueous solution having a pH of from 8 to 8.5 and being at a temperature of about C. to C., passing an electrical current through an inert anode, the electrolyte and the member at a current density of from 5 to amperes per square foot to deposit an adherent coating of uranium oxide over the zinc coating on the member.

2. The process of claim 1, wherein the electrical current is passed through the electrolyte and member until substantially all of the uranium in the electrolyte has been deposited on the surfaces of the member, whereby said desired weight of uranium oxide is applied to the surface thereof.

3. The process of claim 1, wherein .the member comprises aluminum and the zinc coating is applied to the surfaces thereof by applying to its surfaces a strong aqueous solution of sodium hydroxide and zinc oxide.

4. The process of claim 1, wherein the member comprises magnesium, and the zinc coating is applied to the surfaces thereof by electroplating the magnesium member in an aqueous electrolyte comprising essentially from 20 to 60 grams per liter ofzinc, from 20 to grams per liter of alkali metal cyanide and from 30 to 120 grams per liter of alkali metal hydroxide, the ratio of weights of the alkali metal cyanide to the zinc being from 2 to 3, the plating time not exceeding one minute at a current density of at least 40 amperes per square foot of surface.

5. A member comprising a body consisting of a metal selected from the group consisting of magnesium and aluminum, the surface of the member having a first coating composed of zinc of a thinness of less than 0.0001 inch and superimposed thereon an adherent coating of uranium oxide in an amount of up to 5 milligrams per square centimeter, the uranium oxide coating resisting disruption on being subjected to vibration and shock.

References Cited in the file of this patent UNITED STATES PATENTS Hall July 27, 1915 Kahn Jan. 8, 1952 OTHER REFERENCES 

5. A MEMBER COMPRISING A BODY CONSISTING OF A METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM AND ALUMINUM, THE SURFACE OF THE MEMBER HAVING A FIRST COATING COMPOSED OF ZINC OF A THINNESS OF LESS THAN 0.0001 INCH AND SUPERIMPOSED THEREON AN ADHERENT COATING OF URANIUM OXIDE IN AN AMOUNT OF UP TO 5 MILLIGRAMS PER SQUARE CENTIMETER, THE URANIUM OXIDE COATING RESISTING DISRUPTION ON BEING SUBJECTING TO VIBRATION AND SHOCK. 